Insulating bushing for high tension conductors



INSULATING BUSHING FOR HIGH TENSION CONDUCTORS MOTOYUKI OISHI Aug. 18, 1970 v 2 Sheets-Sheet 1 Filed Dec.

INVENTOR.

BYW

g- 1970 MOTOYUKI OISHI 3,5 ,919

INSULATING BUSHING FOR HIGH TENSION CONDUCTORS Filed Dec. 5, 1968 2 Sheets-Sheet 2 FIG. 2

I 30 32 2am United States Patent Int. Cl. H01b 17/26 US. Cl. 174--15 7 Claims ABSTRACT OF THE DISCLOSURE A cylindrical metal casing open on both sides to connect a pair of insulating tube assemblies and having an oil supply valve and oil discharge valve positioned on the upper and lower sides respectively is inserted through a hole bored in the walls, for example, of an indoor substation. A pair of insulating tube assemblies each consisting of an insulating tube embedded in a base member formed of another metal casing and a central conductor housed in said insulating tube are provided, and the openings of both base members, respectively, communicate with both openings of the first-mentioned cylindrical casing with an insulating spacer interposed therebetween. Central conductors encased in the insulating tubes of both base members are connected together by a cable housed in the aforementioned cylindrical metal casing, and the interior of said cylindrical metal casing and those of both base members communicate with each other through an oil path provided on the outside.

BACKGROUND OF THE INVENTION The present invention relates to a wall bushing and more particularly to a wall bushing for use in a super high tension circuit of 500 kv. or over.

A wall bushing is used in leading out a high tension conductor laid in an indoor substation or high tension laboratory, etc. to the outside through the walls of such establishment.

The conventional wall bushing has mostly consisted of an integrally formed linear horizontal type, so that once installed, it presented difficulties in being dismembered. However, due to the recent development of high tension transmission techniques, there has been increasing demand for a wall bushing usable in a circuit having a rated voltage of 500 kv. or over. However, a wall bushing used in a high tension circuit has heretofore unavoidably become long and heavy. For instance, a horizontal type wall bushing (550 kv. in rated voltage, 875 kv. in AC. test voltage and 1,925 kv. at basic impulse level) measured 16 meters in total length, 600 to 700 mm. in the base diameter of an insulating tube and weighed 6 to 8 tons in total. Such elongated and indivisible wall bushing had to be carried by being horizontally placed on the floor of a transport means, for example, a ship or the like. This was economically undesirable because such bushing occupied a large floor space in a transport means. Where the bushing was to be installed in the wall of an establishment such as an indoor substation or high tension laboratory, the whole of it had to be suspended, because it could not be dismembered. This led to the necessity of using a large capacity crane and troublesome handling in fitting. Since the horizontal type bushing was long and heavy, there was further drawback that when it was fitted into the wall, the base of the insulating tube assembly was subject to a great destructive force.

3,524,919. Patented Aug. 18, 1970 SUMMARY OF THE INVENTION The object of the present invention is to eliminate the aforementioned drawbacks encountered in the past and provide a new type of wall bushing which comprises a metal casing to be inserted through a hole bored in the wall of an establishment, a pair of insulating tube assemblies disposed in opposite relationship with the wall lying therebetween and each consisting of an insulating tube embedded in a base member formed of a separate metal casing and a central conductor housed in the insulating tube, the openings of the base members communicating with the respective openings at both ends of the first mentioned metal casing with an insulating spacer interposed therebetween and the central conductors encased in the insulating tubes of both base members being connected together by a cable housed in the aforesaid metal casing. The present invention oifers many advantages, for example, easy dismemberment and reassembly, reducing the floor space to be occupied by the wall bushing when transported, for example, by ship, and permitting easy handling when the bushing is set in place.

BRIEF EXPLANATION OF THE DRAWING FIG. 1 is a lateral view of a wall bushing according to an embodiment of the present invention with a part shown in section:

FIG. 2 is an elevation of an insulating tube dismantled from the bushing body for shipment; and,

FIG. 3 is a lateral view of a wall bushing according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS There will now be described an embodiment of the present invention by reference to FIG. 1. Numeral 2 denotes an entire wall bushing comprising an interconnecting metal casing 11. On the top and bottom sides of said casing 11 are disposed valves 13 and 12 respectively, the objects of which will be described later. The casing 11 has a slantwise rising open section at both ends. The figure illustrates only one, 14, of the open sections. The casing 11 penetrates the hole 16 of the wall 15 of a building and is fixed to the edge of the hole 16 by means of, for example, L-shaped angle steel bars 17.

Numerals 18 and 19 represent a pair of insulating tube assemblies. Since both assemblies are of the same arrangement, the description will be taken only with reference to one, 18, of them. The insulating tube assembly 18 comprises a base member 20 formed of a metal casing and an insulating tube 21 embedded in and rising above the base member 20. As is usually the case, a central conductor 22 extends through the insulating tube 21 and is surrounded with a core 23 made of insulating material The bottom end of the base member 20 is sealed oil tight with an insulating spacer 24. The spacer 24 is intended to keep the central conductor 22 and core 23 at the central position. The insulating spacer 24 is provided with a plurality of concentric annular barriers 25 to increase the radial creeping distance. At the top of the insulating tube 22 is positioned an oil expansion chamber 26.

When the wall bushing 1 Q is fitted to the wall 15, there is initially fixed only the interconnecting casing 11 in the hole 16 of the wall 15. Then the insulating assemblies 18 and 19 are lifted to the fitting position one by one. Into the casing 11 is inserted a cable 31, both ends of which are suitably connected to the bottom end of each of the central conductors 22 of the insulating tube assemblies 18 and 19. The base member 20 of the insulating tube assembly (here reference is only made to 18) is fixed to the edge of the opening 14 of the casing 11 by bolts and nuts 27. The casing 11 and the base member 20 of the insulating tube assembly 18 are connected by pipes 28 and 29 and a valve 30. During the aforementioned fitting operation, however, the valve 30 is not opened at all.

After the wall bushing E has been thus fixed on the wall 15, a valve 12 is connected to an oil source (not shown) and a valve 13 to a vacuum pump (not shown). Initially the casing 11 is evacuated with the valve 12 closed and valve 13 opened. Then oil is introduced from the source into the casing 11 by opening the valve 12. When the casing 11 is fully filled with oil and the oil begins to run out of the valve 13, both valves 13 and 12 are closed and the vacuum pump and oil source are disconnected. The valve 30 is opened to communicate the oil in the casing 11 with that in the insulating tube assembly 18. Thus the entire bushing is serviced with common oil, enabling the expansion and contraction of the oil caused by temperature variations to be compensated for by a free space in the expansion chamber 26.

FIG. 2 represents the state of one, 18, of the insulating tube assemblies which has been dismantled for shipment. The bottom of the insulating tube assembly 18 is sealed oil tight with an insulating spacer 24 and protected with a cover 32.

According to the embidiment of FIG. 3, the wall bushing Q has a long interconnecting casing 33 extending lengthwise through the hole 16 of the wall 15. As illustrated, the insulating tube assemblies 18 and 19 are fitted on the opposite sides of the casing 33 at different heights. To the casing 33 is also connected a conservator 34. This arrangement permits electrical apparatuses located at different ground levels within and without an establishment to be reliably connected by a wall bushing.

As mentioned above, the present invention enables a wall bushing assembly for use in a super high tension circuit to be easily dismembered or reassembled and moreover said assembly to be dismantled to reduced height. Accordingly, each part of the assembly can be carried by ship in a state erected on any of its decks, thus decreasing its occupied floor space and reducing the shipping cost of the assembly.

There are further advantages that when a bushing assembly is to be fitted to the wall of an establishment, dismembered parts can be suspended by a small capacity crane, and so handled with ease. Since the insulating tube is designed to incline upward, a destructive force acting on the base member may be reduced according to the angle of inclination.

What is claimed is:

1. A wall bushing comprising:

a casing mounted in a hole in the wall of an establishment, said casing having open sections on opposite sides of said wall;

a pair of insulating tube assemblies, each including: an elongated insulating tube having a base member fixed to respective open sections of said casing, a central conductor extending through said insulating tube, and an insulating spacer sealing the base member of said insulating tube and holding said central conductor on the axial line of said insulating tube, said insulating tube assemblies inclining upward from opposite sides of said casing;

a conductor in said casing electrically connecting said central conductors of said insulating tube assemblies; and

means for filling at least said casing with a cooling fluid.

2. The wall bushing according to claim 1 wherein the insulating spacer is provided with at least one annular barrier to increase its radial creeping distance.

3. The wall bushing according to claim 1 wherein said casing extends vertically with respect to said wall, one of said open sections being located at the upper part of said casing and the other open section being located at the lower part of said casing on the opposite side of said wall.

4. The wall bushing according to claim 1 wherein said open sections of said casing are inclined.

5. The wall bushing according to claim 4 wherein said open sections are upwardly and outwardly inclined relative to said wall.

6. The wall bushing according to claim 1 comprising means coupled to said casing and to an insulating tube assembly enabling communication of a cooling fluid in said casing with the cooling fluid in said insulating tube assembly.

7. The wall bushing of claim 6 wherein said communication means includes a valve located exterior of said casing and tube assembly.

References Cited UNITED STATES PATENTS 1,777,073 9/1930 Burnham 174-31 2,132,194 10/1938 Skehan ct al. 2,427,184 9/1947 Bilodeau 317l03 X LARAMIE E. ASKIN, Primary Examiner US. Cl. X.R. 174l0, 31 

